Grades K–2 · Materials & Matter
Which material helps keep a toy dry?
Rain can reach a toy from above. A cover keeps the toy dry when it blocks the water's way. The cover must reach over the toy, with no opening above it.
In the diagramPaper testPlastic testWater belowNo water belowPlastic coverWhole cover keeps toy dry here
A whole plastic sheet can send water over its surface instead of letting it pass through. The paper shown here lets water through. These two covers leave the toy different because one blocks the water's path and the other does not.
A hole gives water another way in. Water can fall through the hole even when the plastic around it keeps water out. A useful material cannot close an open gap.
That is why a raincoat needs its hood as well as its fabric. Staying dry depends on where water can go. A good cover puts a barrier all along that route.
About this explanation
The sample results are invented. Different papers, coatings and plastics can behave differently.
Starting knowledge: Compare two pictures and understand wet, dry and a hole in a cover.
Sources
- Next Generation Science Standards — Structure and Properties of Matter: Grade 2